At present, there are known methods of threading the weft thread carriers, consisting in that a weft thread is unwound from a bobbin to be wound in the form of coils by a threadguide onto a spool of a carrier, with the thread introduced into a thread tensioner of the carrier and with its free end gripped prior to winding. After the winding of the thread is completed, the carriers are admitted into a looming-up zone, with a straight section of the weft thread being at the same time formed between this carrier and the threadguide, and as the carrier and the threadguide depart from each other, the weft thread is introduced into the thread tensioner and the straight section thereof is formed. Sequentially, the coils of the weft thread are separated at the edge of the looming-up zone from the straight section.
Apparatus for realizing the known method comprise threadguides arranged on a horizontal rotatable disk and installed so as to be free to rotate around their axes extending parallel to the axis of rotation of the disk for winding the thread, which is unwound from the bobbin, onto the spools of the carriers in the form of coils. Each carrier is provided with a thread tensioner with jaws for gripping the thread, driven into motion by a stationary cam. The apparatus is also provided with a conveyer for propelling the carriers and admitting each of them in succession into the looming-up zone, and with a device for separating the straight section formed when the carriers are being admitted into said zone from the coils.
The threading of the carriers in this known apparatus is as follows.
As soon as the mechanical trajectories of the carriers and the threadguides coincide and the axes of rotation of the spools of the carriers and of the threadguides are aligned, the weft thread of a length sufficient for a pick is wound onto the spools of the carriers due to turning of the threadguides around their axes and due to nipping of the weft thread end by the grips. Now, the weft thread is unwound from the bobbins. Then, the rotation of the threadguides around their axes is stopped, the winding of the weft thread onto the spools of the carriers interrupted and, while the mechanical trajectories of the carriers and the threadguides are diverging, the weft thread is introduced into the thread tensioners of the carriers, whereby a straight section thereof is formed between the thread tensioners of the carriers and the threadguides due to this thread being unwound from the spools of the carriers.
Sequentially, the carriers admit the weft thread into the looming-up zone wherein it is first interlaced with the ending warp threads, while being unwound from the spools of the carriers, and thereafter gripped and cut with the aid of a device located next to the looming-up zone, as a result of which the coils of the weft thread placed on the spools of the carriers are separated from the main reserve thereof on the bobbins.
This known method of threading carriers has the following disadvantages. Due to the introduction of the weft thread into the thread tensioners of the carriers when the mechanical trajectories of the carriers and the threadguides diverge, the reliability of this process is reduced. This is a result of the fact that during this period the spool starts rotating at a variable speed, while the carrier is propelled by the conveyer along the guideways with certain oscillations which renders the weft thread loose, and the latter fails to be engaged by the thread tensioner of the carriers.
Additionally, with this threading being performed at different mechanical trajectories of the carrier and the threadguide, the latter must be strictly oriented relative to the carrier by being positioned in a definite zone in front of the thread tensioner. Otherwise, the threadguide, while operating, may bump into the body of the carrier or the thread tensioner. Such a strict orientation requires that the accuracy of manufacture of the drive of the threadguide and the carriers, as well as the accuracy of mechanical trajectories thereof, be increased.
Formation of the straight section of the weft thread, with the mechanical trajectories of the carriers and the threadguides diverging, due to unwinding of the thread from the spools of the carriers before the latter enter the looming-up zone requires that during each cycle of winding the amount of the weft thread wound onto the spools of the carriers be greater than necessary for forming the cloth. This makes it necessary to increase both the speed of rewinding of the weft thread and the capacity of the carrier spools and, therefore, the size thereof.
Interlacing of the weft thread with the edging warp threads before the former is gripped and cut near the looming-up zone renders the selvage of the cloth slack due to the overdosage of the weft thread caused by the fact that the latter, while being interlaced with the warp threads, is disposed at a great angle to the fell of the cloth, and the tension applied thereto markedly decreases in the process of displacement thereof towards the fell.
It is an object of the present invention to provide a method of and an apparatus for threading the weft thread carriers, which will ensure reliable engagement of the weft thread by the thread tensioner.
The principal object of the invention is to reduce the breakage rate of the weft thread during winding.